20/20 Vision: The visual acuity in the optically ‘normal’ human eye. The top number indicates that the acuity is tested at a distance of twenty feet from the eye to the chart. The bottom number indicates the size of letter or symbol that the eye can see at that distance. Deviations from the norm are expressed by changing the bottom number to be larger or smaller than 20. Numbers larger than 20 represent larger sizes of letters or symbols whereas numbers smaller than 20 represent smaller sizes of letters or symbols. For example, a person with 20/30 vision sees a size of letter at twenty feet that an optically ‘normal’ eye can see at thirty feet.***
Visual Acuity: The ability of the eye to resolve detail. Normal visual acuity is 20/20.
Amblyopia (Lazy Eye): There are many conditions, such as crossed eye, nearsightedness or farsightedness, that can lead to the development of amblyopia, commonly referred to as lazy eye. Regardless of the condition that causes amblyopia, one or both eyes does not have clear vision, even with glasses or contact lenses.
Children or adults suffering from amblyopia typically don’t develop the concept of opposites, and may have difficulty keeping their balance, especially in sports. Traditionally, patching is used to treat amblyopia. However, studies have shown that combining Vision Therapy with patching is a more effective treatment.
Convergence: The turning in of the two eyes when one looks from far to near.**
Convergence Insufficiency: A disorder in which the individual does not aim the eyes at the same point in space, particularly when viewing a near target.**
Depth perception: The use of visual information from one or both eyes to determine spatial relationships between viewed objects.**
Developmental Optometrist: A developmental optometrist treats functional vision problems, including difficulties with binocular vision, eye movements and depth perception, as well as visual deficits following brain injuries. These optometrists are skilled in the use of lenses, prisms and optometric vision therapy and provide vision care based on the principle that vision can be developed and changed. **
Divergence: The turning out of the two eyes when one looks from near to far.**
Hyperopia (Farsightedness) – A visual condition in which distant objects are usually seen clearly, but near objects do not come into proper focus.
Learning-related Vision Problems – Vision disorders that interfere with reading and learning.*
Myopia (Nearsightedness): A visual condition in which near objects are seen clearly, but distant objects are blurred.*
Ophthalmologist – M.D. : An ophthalmologist is a medical or osteopathic doctor who receives residency training and specializes in the diagnosis and treatment of eye disease. In general, ophthalmologists use medical and surgical methods to treat eye diseases and vision disorders.
Optician: A licensed technician who makes and dispenses eyeglasses according to prescriptions from optometrists and ophthalmologists. ***
Optometrist – O.D. : Doctors of optometry (O.D.s) are the primary health care professionals for the eye. Optometrists examine, diagnose, treat, and manage diseases, injuries, and disorders of the visual system, the eye, and associated structures as well as identify related systemic conditions affecting the eye.
An optometrist completes a pre-professional undergraduate education at a college or university and then completes four years of professional education at a college of optometry. Upon graduating, an optometrist can complete an optional one year residency for additional training in a specific area of practice.
Snellen chart: A chart imprinted with rows of black letters, with the letters graduating in size from smallest on the bottom row to the largest on the top row. It was developed by Dutch ophthalmologist Herman Snellen (1834-1908), and is used for testing visual acuity.***
Stereopsis (‘3D vision’): The sensation of three dimensional depth created by the brain combining the two slightly different images obtained from each of the two eyes.***
Strabismus (Crossed Eye): Commonly referred to as cross-eye or wall-eye, this condition occurs when the two eyes don’t work together. One of the two eyes will turn in a different direction than the other (either in or out), which is the result of poor eye muscle control.
It is normal for a baby to occasionally experience strabismus during the first 3 ½ months of life. If the condition persists, care may be required. The condition can also develop as children reach school age.
Ophthalmologists may recommend surgery to correct this condition. Surgical correction of strabismus involves cutting the muscles that control the eye in order to make the eye appear straight. However, this does not solve the underlying problem: The eyes have not developed the ability to work together. Vision therapy offers a functional cure by training the eyes to work as a team.
*American Optometric Association
** Fixing my Gaze, by Dr. Susan Barry
*** Smart Medicine for Your Eyes, by Dr. Jeffrey Anshel